Bent capillary tube aerosol generator

ABSTRACT

An apparatus for generating aerosol comprises a capillary tube comprising at least one bend, fluid inlets, and an outlet along the bend. The capillary tube is heated to a temperature sufficient to volatilize fluid in the capillary tube, such that the volatilized fluid discharges from the outlet to form an aerosol.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. 119 to U.S.Provisional Patent Application No. 60/763,350 filed on Jan. 31, 2006,the entire content of which is hereby incorporated by reference.

SUMMARY

Aerosols are useful in a wide variety of applications. For example, itis often desirable to treat respiratory ailments with, or deliver drugsby means of, aerosol sprays of finely divided particles of liquid and/orsolid, e.g., powder, medicaments, etc., which are inhaled into apatient's lungs. Aerosols are also used for purposes such as providingdesired scents to rooms, distributing insecticides and delivering paint,fuel and lubricant.

Provided is an aerosol generator in the form of a capillary tube, thecapillary tube comprising at least one bend, fluid inlets, and an outletalong the bend, wherein volatilized fluid expands out of the outlet andmixes with ambient air to form an aerosol. The fluid inlets may belocated at ends of the capillary tube. The capillary tube may comprisemore than one bend, e.g., plural bends in the same plane or the tube maybe coiled. The aerosol generator may comprise a source of liquid influid communication with the fluid inlets. The capillary tube may be 5to 40 millimeters, preferably 10 to 25 millimeters, long and has aninner diameter of 0.1 to 0.5 millimeters, preferably 0.1 to 0.2millimeters.

Also provided is an aerosol generator comprising a capillary tubecomprising at least one bend, fluid inlets, and an outlet along the bendand a heating mechanism which heats the capillary tube to a temperaturesufficient to volatilize fluid in the capillary tube. The capillary tubecan be made of an electrically resistive heating material such asstainless steel and the heating mechanism can be a power supply withleads attached to the capillary tube to pass electrical current at leastalong the bend to heat the capillary tube to a temperature sufficient tovolatilize fluid in the capillary tube. The aerosol generator mayfurther comprise a mouthpiece and/or a source of fluid.

Further provided is a method for generating an aerosol, comprising thesteps of supplying fluid to an aerosol generator comprising a capillarytube comprising at least one bend, first and second fluid inlets and anoutlet along the bend and heating the capillary tube to heat the fluidto a temperature sufficient to volatilize the fluid to form a volatizedfluid, such that the volatilized fluid expands out of the outlet of thecapillary tube, the volatilized fluid mixing with ambient atmosphericair to form an aerosol. The outlet is preferably equidistant from thefirst and second fluid inlets. Fluid may be supplied to the first andsecond fluid inlets at identical or different flow rates. Identical ordifferent fluids, which may be liquids, may be supplied to the first andsecond fluid inlets. A liquid may be supplied to a first fluid inlet anda gas may be supplied to a second fluid inlet. Fluid supplied to thecapillary tube may comprise tobacco extracts and a carrier solutionand/or at least one medicament.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a fluid vaporizing device.

FIG. 2 is a schematic representation of a bent capillary tube portion ofthe device shown in FIG. 1.

FIG. 3 provides an enlarged view of the bent capillary tube, with FIG. 3a providing a front view, FIG. 3 b providing a top view, and FIG. 3 cproviding a magnified view of the outlet of the capillary tube.

FIGS. 4 a-c provide perspective views of the bent capillary tubeconnected to and extending through an electronics driver printed circuitcard with a controller, with FIG. 4 a providing a front view, FIG. 4 bproviding a side view, and FIG. 4 c providing a top view.

FIGS. 5 and 6 show additional embodiments of the bent capillary tube.The bent capillary tube of FIG. 5 includes multiple bends and the bentcapillary tube of FIG. 6 includes a coiled tube having multiple bends.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Provided is a fluid vaporizing device useful for applications includingaerosol generation. The device includes a bent capillary tube or passagewhich can be heated by passing electrical current therethrough, andthrough which fluid flows to be at least partially vaporized and ifdesired to generate an aerosol. Preferably, the bent capillary passagecomprises an arcuate passage portion and an outlet at a location alongthe arcuate passage. In order to heat the tube, an electrical currentsupplied by a first electrode at one inlet end of the tube passes alongthe tube to a second electrode at the other inlet end of the tube. Fluidfrom the same or different sources can be supplied as a pressurizedliquid at the inlets and is at least partially converted to a vapor bythe input of heat generated by resistance heating from the flow ofelectricity along the tube as the fluid flows from the inlet endsthrough the tube toward the outlet. When used as an aerosol generator ofan inhaler, such as a hand-held inhaler for aerosolizing medicaments orflavor substances, as the vapor exits from the tube at the outlet of thecapillary tube an aerosol is produced as the vapor enters thesurrounding atmosphere.

In a preferred embodiment, the bent capillary tube comprises at leastone bend (or arcuate portion), such as a 180° bend, such that the inletends of the tube are equidistant from the outlet of the tube. Thus, asthe bent capillary tube has more than one path (e.g., two legs) throughwhich fluid travels from the inlets ends of the tube to the outlet, thebent capillary tube provides for a very compact structure compared to anaerosol generator comprising a linear capillary tube having a singlepath through which fluid travels from inlet to outlet. Further, comparedto an aerosol generator comprising a capillary tube having a single paththrough which fluid travels from inlet to outlet, the pressure requiredto move fluid through the two legs of the bent capillary tube is lowerto achieve a targeted flow rate. Conversely, for a targeted flow rate ofaerosol, the flow rate of fluid traveling through each leg of the tubeis slower. As a result of a slower flow rate of fluid traveling throughthe two legs of the tube, heat is transferred more efficiently from thetube into the fluid, less energy is required to vaporize (volatilize)liquid flowing through the tube, and the footprint of the tube may bereduced. Preferably, sufficient heat is transferred to vaporize all ofthe liquid entering the bent capillary by the time the fluid arrives atthe outlet.

As the bent capillary tube has more than one inlet, an aerosolcomprising more than one fluid may be formed. More specifically,different liquids, which may not mix well, may be fed into respectiveinlet ends of the tube. Alternatively, an aerosol comprising liquid andgas may be formed by feeding liquid into, for example, one inlet end ofthe tube and gas into, for example, the other inlet end of the tube.Further, a carrier solution containing tobacco extracts or tobaccoflavor constituents may be used to form an aerosol, with the resultingaerosol having organoleptic attributes similar to tobacco smoke.

Preferably, the temperature of the tube and the fluid are greatest atthe outlet and preferably, the outlet is at the center of the bend inthe tube, (e.g., is preferably equidistant from each inlet end of thetube and preferably equidistant from each electrode), and the outletpreferably has a diameter approximately equal to the inner diameter ofthe bent capillary tube. However, if different fluids are fed into eachinlet end of the tube, in order to optimize aerosol generation, it maybe preferable that the outlet not be equidistant from each inlet end ofthe tube or equidistant from each electrode and/or the electrode not belocated in identical positions on respective paths from the inlet endsof the tube to the outlet. Further, if different fluids are fed intoeach inlet end of the tube, in order to optimize aerosol generation, itmay be preferable that the different fluids be fed at different flowrates.

The capillary tube can be made entirely from an electrically conductivematerial, such as stainless steel, so that as a voltage is applied to alength of the tube, the tube is heated by the flow of electrical currentthrough the tube, and the fluid passing through the tube is vaporized.As an alternative, the tube could be made from a non-conductive orsemi-conductive material, such as glass or silicon, with a coating orlayer of resistance heating material such as platinum for heating thetube. Specifically, the tube could be fused silica with heater elementformed by a resistive coating.

Provided is an improvement to a single capillary tube arrangement usedto vaporize fluid wherein heat loss can occur at an electrical leadnearest the capillary tube exit and cause a dramatic decline intemperature along the capillary tube toward the tip. To compensate forsuch heat loss and maintain the tip at a temperature sufficiently highfor the generation of a quality aerosol, the capillary midsection may beoverheated. This overheating exposes the fluid to be aerosolized tounnecessarily high temperatures which can, in some cases, be sufficientto cause thermal degradation of fluid constituents.

FIG. 1 shows an embodiment of a fluid vaporizing device in the form ofan aerosol generator 10 for use as a hand held inhaler. As shown, theaerosol generator 10 includes a source 12 of fluid, a valve 14, a heaterarrangement comprising a bent (or hairpin) capillary tube 20, amouthpiece 18, an optional sensor 15 and a controller 16. The controller16 includes suitable electrical connections and ancillary equipment suchas a battery which cooperates with the controller for operating thevalve 14, the sensor 15 and supplying electricity to heat the bentcapillary tube 20. In operation, the valve 14 can be opened to allow adesired volume of fluid from the source 12 to enter the bent capillarytube 20 prior to or subsequent to detection by the sensor 15 of apressure drop in the mouthpiece 18 caused by a smoker/patient attemptingto inhale aerosol from the aerosol generator 10. As fluid is supplied tothe bent capillary tube 20, the controller 16 controls the amount ofpower provided to heat the capillary tube sufficiently to volatilizefluid in the bent capillary tube 20, i.e., the controller 16 controlsthe amount of electricity passed through the capillary tube to heat thefluid to a suitable temperature for volatilizing the fluid therein. Thevolatilized fluid exits an outlet of the bent capillary tube 20, and thevolatilized fluid forms an aerosol which can be inhaled by a person uponhis/her drawing upon the mouthpiece 18.

The aerosol generator shown in FIG. 1 can be modified to utilizedifferent fluid supply arrangements. For instance, the fluid source cancomprise a delivery valve which delivers a predetermined volume of fluidto the bent capillary tube 20 and/or the bent capillary tube 20 caninclude one or more metering chambers of predetermined size toaccommodate a predetermined volume of fluid to be volatilized during aninhalation cycle. In the case where the bent capillary tube 20 includesone or more metering chambers to accommodate a volume of fluid, thedevice can include a valve or valves downstream of the chamber(s) forpreventing flow of the fluid beyond the chamber(s) during fillingthereof. If desired, the chamber(s) can include a preheater arranged toheat fluid in the chamber(s) such that a vapor bubble expands and drivesthe remaining liquid from the chambers into the bent capillary tube 20.Details of such a preheater arrangement can be found in commonly ownedU.S. Pat. No. 6,491,233, the disclosure of which is hereby incorporatedby reference. Alternatively, fluid in the chamber(s) could be preheatedto a set temperature below vapor bubble formation. If desired, thevalve(s) could be omitted and the fluid source 12 can include a deliveryarrangement such as one or more syringe pumps which supply apredetermined volume of fluid directly to the bent capillary tube 20. Inthe case where the bent tube is made of an electrically conductivematerial such as stainless steel, the heating arrangement can be aportion of the capillary tube defining bent capillary tube 20, arrangedto volatilize the liquid in bent capillary tube 20. The sensor 15 can beomitted or bypassed in the case where the aerosol generator 10 isoperated manually by a mechanical switch, electrical switch or othersuitable technique. Although the aerosol generator 10 illustrated inFIG. 1 is useful for aerosolization of inhalable aerosols, such as drugor flavor bearing aerosols, the bent capillary tube can also be used tovaporize other fluids such as, for example, odorants, insecticides,paint, lubricants, and fuels.

A bent capillary tube aerosol generator may receive fluid flow from asingle fluid source. A fluid, generally in the form of a pressurizedliquid and/or predetermined volume of fluid from the same or separatefluid sources, enters through the inlets of the capillary tube and flowsthrough the legs of the tube towards the outlet of the tube. Preferablya separate electrode is provided at each inlet end of the capillarytube. The portion of the capillary tube between the electrodes is heatedas a result of the electrical current flowing through a portion of thetube between the electrodes, and the liquid entering the inlet ends isheated within the tube to form a vapor. As the vapor exits from theoutlet of the capillary tube and comes into contact with the surroundingambient air, the vapor forms an aerosol. If the liquid is a suspension,the aerosol can be formed from solids in the suspension. If the liquidis a solution of a condensable liquid, the aerosol can be formed fromdroplets of condensed vapor. If the outlet is smaller in cross-sectionthat the internal diameter of the capillary tube, the aerosol can beformed from atomized liquid driven through the outlet by vaporizedliquid.

As shown in FIG. 2, a fluid vaporizing device includes a capillary tube20, with a fluid from a fluid source 22 passing through the capillarytube 20. The fluid enters the capillary tube 20 at first inlet end 20 aand second inlet end 20 b, and exits as a vapor from the outlet 20 c ofcapillary tube 20. A first electrode 23 a is connected near the inletend 20 a of capillary tube 20, and a second electrode 23 b is connectednear the inlet end 20 b.

A liquid entering at the inlet 20 a of capillary tube 20 and inlet 20 bis heated as it passes through the capillary tube. Sufficient heat isinput to the fluid passing through the tube to vaporize at least some ofthe fluid as it exits from the outlet 20 c of the capillary tube. Again,while not illustrated but as indicated above, the aerosol generator mayinclude more than one fluid source for each inlet of the bent capillarytube.

FIGS. 3 a-b illustrate an enlarged view of the bent capillary tube 30.FIG. 3 a provides a top view of the bent capillary tube 30, in whichfluid enters at first inlet end 30 a and second inlet end 30 b, andexits as a vapor from the outlet 30 c in a semicircular bend incapillary tube 30. A first electrode 33 a is connected near the inletend 30 a of capillary tube 30, and a second electrode 33 b is connectednear the inlet end 30 b. FIG. 3 b illustrates a front view of the bentcapillary tube, and FIG. 3 c provides a magnified view of the outlet ofthe capillary tube.

FIGS. 4 a-c illustrate perspective views of the bent capillary tube.Specifically, FIG. 4 a provides a top view of the bent capillary tube,which is connected to and extends through the electronics driver printedcircuit card 49 with a controller 46, FIG. 4 b provides a side view ofthe bent capillary tube, which is connected to the electronics driverprinted circuit card and controller, and FIG. 4 c provides a front viewof the bent capillary tube, which is connected to the electronics driverprinted circuit card and controller. The legs of the bent capillary tubeare preferably connected to the electronics driver printed circuit cardby a conductive adhesive, such as, for example, solder or conductiveepoxy, allowing the electronics driver printed circuit card to supplyelectricity to the legs of the bent capillary tube to heat the bentcapillary tube.

Additional embodiments of the bent capillary tube are schematicallyshown with reference to FIGS. 5 and 6. The bent capillary tube of FIG. 5includes multiple bends 51 a, 51 b, 51 c, preferably have a singleoutlet along the centermost bend 51 b. The bent capillary tube of FIG. 6includes a coiled tube having multiple bends 61 a, 61 b, 61 c, 61 d, 61e, preferably have a single outlet in the centermost bend 61 c.

The bent capillary tube arrangement is designed to accommodate a varietyof liquid flow rates through the capillary tube, is highly energyefficient and provides a compact arrangement. In inhaler applications,the heating zones of the capillary tube can be 5 to 40 millimeters long,or more preferably 10 to 25 millimeters long, and the inner diameters ofthe tube can be 0.1 to 0.5 millimeters, or more preferably 0.1 to 0.2millimeters. In implementing the capillary heater in an inhaler, thebent capillary tube arrangement is preferably insulated and/or isolatedfrom ambient air and the vapor emitted from the capillary tube. Forexample, a body of insulating material could be used to support the bentcapillary within a mouthpiece such that the vapor exiting the capillarytube does not contact the outer surface of the capillary tube.

The direction of discharge from the capillary is disclosed in FIG. 3 asbeing oriented in a direction within the general plane of the capillaryaway from the end of portions of the capillary. In the alternative, thedischarge may instead be in a direction within the general plane of thecapillary toward the end of portions of the capillary or in a directionoutside of the general plane defined by the capillary, such as adirection that is orthogonal to the general plane defined by thecapillary.

While various embodiments have been described, it is to be understoodthat variations and modifications may be resorted to as will be apparentto those skilled in the art. Such variations and modifications are to beconsidered within the purview and scope of the claims appended hereto.

1. An aerosol generator in the form of a capillary tube, the capillarytube comprising at least one bend, fluid inlets, and an outlet along thebend, wherein volatilized fluid discharges from the outlet to form anaerosol.
 2. The aerosol generator of claim 1, wherein the fluid inletsare located at ends of the capillary tube.
 3. The aerosol generator ofclaim 1, wherein the capillary tube comprises more than one bend.
 4. Theaerosol generator of claim 1, further comprising a source of liquid influid communication with the fluid inlets.
 5. The aerosol generator ofclaim 1, wherein the capillary tube is 5 to 40 millimeters long and hasan inner diameter of 0.1 to 0.5 millimeters.
 6. The aerosol generator ofclaim 1, wherein the capillary tube is 10 to 25 millimeters long and hasan inner diameter of 0.1 to 0.2 millimeters.
 7. An aerosol generatorcomprising: a capillary tube comprising at least one bend, fluid inlets,and an outlet along the bend; and a heating mechanism which heats thecapillary tube to a temperature sufficient to volatilize fluid in thecapillary tube.
 8. The aerosol generator of claim 7, wherein thecapillary tube is made of electrically resistive heating material andthe heating mechanism comprises a power supply and leads attached to thecapillary tube such that current passes along the bend and heats thecapillary tube to a temperature sufficient to volatilize fluid in thecapillary tube.
 9. The aerosol generator of claim 7, further comprisinga mouthpiece.
 10. The aerosol generator of claim 7, further comprising asource of fluid.
 11. A method for generating an aerosol, comprising thesteps of: supplying fluid to an aerosol generator comprising a capillarycomprising at least one bend, first and second fluid inlets and anoutlet along the bend; and heating the capillary to heat the fluid to atemperature sufficient to volatilize the fluid to form a volatizedfluid, such that the volatilized fluid discharges from the outlet of thecapillary to form an aerosol.
 12. The method of claim 11, wherein theoutlet is equidistant from the first and second fluid inlets.
 13. Themethod of claim 11, wherein fluid is supplied to the first and secondfluid inlets at identical flow rates.
 14. The method of claim 11,wherein fluid is supplied to each of the fluid inlets at different flowrates.
 15. The method of claim 11, wherein identical fluids are suppliedto the first and second fluid inlets.
 16. The method of claim 11,wherein different fluids are supplied to the first and second fluidinlets.
 17. The method of claim 11, wherein identical liquids aresupplied to the first and second fluid inlets.
 18. The method of claim11, wherein different liquids are supplied to the first and second fluidinlets.
 19. The method of claim 11, wherein a liquid is supplied to thefirst fluid inlet and a gas is supplied to the second fluid inlet.
 20. Amethod of generating an aerosol comprising: discharging a volatilizedsystem from a location along a capillary passage by introducing avolatile liquid into each of opposite end portions of the capillarypassage and volatilizing at least a portion of the liquid prior to thedischarging step.
 21. A method of claim 20, wherein the discharging isfrom a location along an arcuate portion of the capillary passage.